Heat Stress: Not a Problem Until Someone Dies?

Along with education, risk assessment, providing liquids, and PPE, consider cooling garments and adjust individuals' work and rest regimens.

IN the world of occupational heat stress, including professional sports such as American football, employers and employees must find some accommodation between reasonable productivity and reasonable heat stress illness prevention. Unlike exposure to some occupational hazards, such as noise and vibration, the nature of heat stress illness is that it sometimes can come on quickly with little warning, and once it is experienced, the consequences can be deadly. In that way, heat stress hazards are more like toxic gas hazards in the workplace.

Deadly Combinations
As a weather event, heat kills more people in the United States (averaging 200 per year) than the next two weather events, floods and tornadoes, combined.1 During a European heat wave in the summer of 2003, more than 14,800 people died from the heat in France alone.2

Agricultural workers are exposed to these weather risks, especially when they are wearing protective clothing to prevent pesticide exposure. When hot weather is combined with process-related heat, such as in foundries, bakeries, glass plants etc., the combined effect is difficult to protect against. Firefighters, too, are habitually exposed to heat stress dangers, and there are documented cases where they have died as a result of heat stress.3

Existing Guidelines
Unfortunately for those working in hot environments in the United States--except for all military branches, which have WBGT (Wet Bulb Globe Temperature) rules--there are not OSHA or EPA regulations to follow. There are guidelines, however, put out by the American Conference of Governmental Industrial Hygienists (ACGIH).

These are Threshold Limit Values (TLVs) that take into account environmental measurements, different types of personal protective equipment the worker may be wearing, the workload, and acclimatization in order to prescribe work/rest regimens.

Several ISO documents related to heat stress are followed closely in Europe and other places. There is ISO 7726, which has to do with instruments and methods; and ISO 8996, which has to do with ergonomics and thermal environments.

OSHA citations involving heat stress are prosecuted under the General Duty Clause. These types of citations may originate from employee complaints or may be discovered if OSHA is on location for another reason and notices heat stress problems. Naturally, employers want to stay away from exposure to these citations. However, the liabilities for a heat stress death don't stop with General Duty Clause citations and the fines that often follow.

In different jurisdictions, employers also can be found liable in criminal and civil actions for unlawful death. Canadian law was just changed to provide criminal penalties for executives who don't provide a sufficiently safe workplace. The family of the late Korey Stringer, a lineman with the Minnesota Vikings football team, sued the Vikings for more than $100 million in connection with his untimely death from heat stress during preseason practice.4 The results of these accidents in U.S. jurisprudence could even be jail time for company officers and insolvency of the enterprise where an untimely, heat stress-related death occurred.

The System
Given the huge downside for ignoring heat stress in the workplace, the prudent thing to do is to design and implement a robust system for screening and warning workers in dangerous heat stress environments. Such a system should include employee health screening prior to placement in a high heat stress condition.

This can be done with interviews or questionnaires and should cover such questions as the employee's previous exposure to heat-related illness (because previous exposure may compound the risk for subsequent exposure); the employee's self-rating of his overall health at the time and his overall physical condition, and observations about the clothing the employee is wearing.

This should be supplemented with education on the risks of heat stress illness, how to recognize it, and how to deal with its onset. Workers laboring without protective clothing often can hydrate themselves with water or commercially available beverages designed to combat heat stress, and making these available should be considered. Study the nature of the work so as to minimize the heat stress risks, and apply labor-saving devices to the job as appropriate.

After this is done, it's time to consider cooling garments and instrumentation that will provide the employer with information on which to base individual work and rest regimens.

WBGT and Personal Heat Stress Monitors
The generally accepted method for measuring heat stress risk on an area-wide basis is the WBGT method. Even in sports medicine within the United States, WBGT has been recognized by the National Athletic Trainers' Association (NATA) as the gold standard for qualifying the risk of heat illness.5

It is a measurement, done by a specially designed instrument, which takes into consideration the various environmental factors all workers in a particular environment are facing: ambient temperature, relative humidity, air flow, and radiant heat. A wet bulb sensor gives a humidity reading, the globe sensor gives a radiant heat reading, and a dry bulb thermometer gives an ambient temperature reading. Those three readings are combined using an algorithm developed to correlate to expected human physiological response under different combinations of individual sensor readings.

The output is a "WBGT index" reading, expressed in degrees Celsius or Fahrenheit. After some experimentation following ACGIH, NATA, U.S. armed services, or ISO guidelines, an employer generally can make a determination as to what figures of WBGT degrees to use to take different courses of action.

"Work rest regimens" have been prescribed by ACGIH based on research work. These can be used if desired to give workers more rest breaks as the WBGT reading gets hotter. The particular problem some employers vocalize is that these guidelines are purposefully vague because they must cover a wide range of humans. As a result, strict adherence to these guidelines may inhibit the employer from getting the most safe productivity that can be had from its workforce. This can be the case if the workforce is in good physical health, has been properly acclimated by virtue of working in the same high-heat environment for several days or weeks without a problem, and has access to beverages for hydration.

However, if there were a heat stress fatality under such conditions, the employer would be on thin ice in a legal sense trying to defend itself unless it had very good documentation.

One method that seems to have some merit is to use personal heat stress monitors on workers who are new to the workforce or to the high heat stress job until they become trained and acclimated. A variant is to use personal heat stress monitors on select workers who are thought or known to be at risk for heat stress, such as obviously out-of-condition football players who show up for summer training camp. Personal heat stress monitors are devices that alarm to warn individual workers their core body temperature is approaching a preset maximum. These devices are not foolproof and must be properly used, worn, and calibrated prior to use. They can provide a first line of defense for employees at specific risk, even when the WBGT area measurement might suggest it is safe to work in such an environment.

Smart employers will want to maintain records of employee exposures. The area instruments can log that data (and can present it in real time on a Web page if desired), while the personal instruments can log personal exposure data.

The Trade-Off
It's obvious that with the pressures on cost and productivity in today's working environment, employers want to keep employees working as long and fast as possible. However, when the costs of even one serious heat stress accident or fatality are expressed, it becomes obvious employers can and should invest in assuring their workers are safe from even the remotest chance of a fatal heat stress injury.

Such assurance can be had by training and screening individual workers, allowing all workers appropriate work-rest cycles, having the foresight to use the heat stress instruments that are available for worker protection, and keeping logged data.

Used as part of a heat stress prevention program, WBGT monitors, together with personal heat stress monitors, can provide valuable safeguards to ensure those who work in hot environments don't succumb to heat stress. They can help allow safe worker productivity worth well more than their cost, especially if a potentially fatal heat stress accident is avoided.

1. National Weather Service Forecast Office, "Are You Ready for Summer?" www.srh.noaa.gov/shv/Heat_Awareness.htm.
2. Associated Press, 2003 by Pamela Sampson, as published in The Guardian (UK) and FreeRepublic.com,
3. California FACE report No. 97CA01001, October 19, 1997, www.cdc.gov/niosh/face/stateface/ca/97ca010.html.
4. msn.espn "Stringer family to seek more than $100M in damages," 11/8/2001, http://msn.espn.go.com/nfl/news/2001/1107/1274703.html.
5. National Athletic Trainers' Association Position Statement: Exertional Heat Illness, Journal of Athletic Training 2002;37(3);329-343.

This article originally appeared in the March 2004 issue of Occupational Health & Safety.

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